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Glossary of Terms

AGL — Abbreviation for Above Ground Level
AIRFRAME — metal frame of a hang glider that supports sail. Made up of tubing, cables, plates and bolts.
AIRFOIL — shaped wing section, designed to provide lift.
AIRSPEED — speed at which a glider passes through the air.
ARSA — abbreviation for Airport Radar Service Area.
ASI — Abbreviation for Airspeed Indicator.
ALTIMETER — instrument that measures altitude.
ATTITUDE — orientation of the glider in the pitch, roll or yaw axes.
AN — abbreviation for Aircraft Nomenclature. Designation stamped on hardware to specify that it's of aircraft quality.
ANGLE OF ATTACK — pitch angle at which the wing meets the air passing over it.
APEX — area at the top of the glider's triangular control bar.
APPROACH — planned path a glider flies toward landing area. Most common type — Standard Aircraft Approach.
ASPECT RATIO — measure of how long and narrow a wing is. Determined by dividing a wing's span by its average chord.
BACK UP — secondary hang loop used as precaution in case main loop fails during flight.
BASE LEG — segment of glider's landing approach. Precedes final leg.
BASE TUBE — tube that forms bottom of glider's triangular control bar. Pilot's hands rest on base tube during flight.
BATTEN — formed rib that slips into sail to define airfoil shape.
BEAK IN — bungling landing flare so that nose of glider "beaks" against ground.
BEST GLIDE SPEED — airspeed at which a glider achieves best glide ratio.
BLUE THERMAL — thermal that is not marked by characteristic cumulus cloud.
BOOMER — strong thermal.
BUNGEE — elasticized cord used to fasten battens and other glider parts.
CAMBER — cross sectional curvature of an airfoil.
CARABINER — locking metal link used to attach harness to hang loops.
CG — abbreviation for Center of Gravity. Point at which the pilot is suspended from the glider.
CHORD — distance from leading to trailing edge of a wing.
CLOUDBASE — altitude of cloud bottoms.
CLOUDSTREET — cumulus clouds aligned in 11 streets" by wind. Excellent for long crosscountry flights.
COCOON — soaring harness that encloses and supports pilot from shoulders to toes.
CONTROL BAR — triangular frame the pilot uses to launch, land and control the glider. Made up of down tubes and base tube.
CONTROLLED AIRSPACE — area in which services to pilots are provided by FAA. Marked on air sectional charts.
COORDINATION — blending of pitch and roll inputs to produce smooth turn.
CRABBING — angling glider to counteract the effect of wind drift.
CROSS—CONTROLLING — incorrect weightshift technique that cancels effect of pilots' control inputs.
CROSSBARS — main glider structural members that run between keel and leading edges. Hidden inside sail on double—surface gliders.
CU — abbreviation for Cumulus. Puffy white cloud that often indicates thermal lift.
CU-NIM — short for Cumulo-Nimbus. Dangerous, anvil-shaped thunder cloud.
CZ — abbreviation for Control Zone.
DACRON — trade name. Synthetic material used to make glider sails.
DAMPING — tendency of a glider to resist change in direction or motion.
DIHEDRAL — upward angling of wing tips to make glider more stable in roll.
DIVERGENCE — tendency for glider to increase steepness of dive. Indicates dangerous lack of pitch stability.
DOUBLE SURFACE — glider with upper and lower sail surfaces that enclose airframe to reduce drag and improve performance.
DOWN TUBES — angled vertical tubes that form sides of control bar.
DRAG — aerodynamic resistance force that tries to hold glider back as it flies.
FAA — abbreviation for Federal Aviation Administration. Federal agency responsible for regulating aviation in the U.S.
FAIRING — shaped enclosure or covering designed to smooth airflow and reduce drag.
F.A.R. — abbreviation for Federal Aviation Regulation.
FINAL — final segment of landing approach as glider heads for landing spot.
FLARE — raising the nose sharply to stall the glider for landing.
FRONT — boundary between air masses of different temperature and pressure.
G — short for Gravity. Refers to loading experienced by pilot and aircraft in flight. G-loading increases during sharp maneuvers.
GLIDE RATIO — angle at which glider descends through air. Determined by how much lift and drag a particular wing produces.
GROUND EFFECT — tendency of a glider to glide farther when flying close to the ground.
GROUND SPEED — speed at which the glider passes over the ground.
HAND FAIRINGS — insulated mitts that slip over glider's base tube. Pilot can insert hands for warmth.
HANG CHECK — hanging in harness while attached to glider before launch to check suspension system and ensure that pilot has hooked in.
HANG STRAP — suspension strap the pilot hooks in to before launch. (There are always two hang straps — a main and a back up.)
HGMA — abbreviation for Hang Glider Manufacturers Association.
INVERSION — weather condition i in which warm air is trapped aloft, inhibiting thermal development.
KEEL — main structural tube that runs along sail at center chord of wing.
KINGPOST — vertical strut on top of glider that supports negative rigging and luff line systems.
KNEE HANGERS — supports used to hold up pilot's legs on some harnesses.
LAPSE RATE — rate at which the air cools with altitude change.
LEADING EDGE — front edge of the wing.
LIFT — rising air.
LIFT TO DRAG RATIO — amount of lift and drag produced by a wing. Determines a glider's glide ratio.
LOG BOOK — book that records a pilot's flights. Documents experience and accomplishments.
LUFF LINES — lines running from kingpost to trailing edge. Aid to dive recovery.
MINIMUM SINK SPEED — speed at which glider descends most slowly through the air. Often abbreviated as "min. sink."
MSL — abbreviation for Mean Sea Level. Height above sea level.
MYLAR — Trade name. Smooth plastic material used as stiffener in hang glider sails.
NICOPRESS — oval metal slug used to clamp cables.
NOSE ANGLE — angle of leading edges to each other when viewed from above or below.
NOSE PLATE — metal plate at junction of keel and leading edges.
NYLOC — nut with elastic nylon insert that prevents it from unthreading by accident.
PITCH — Nose up or down attitude. Controlled by shifting of pilot's weight to front or rear.
POD — fully-enclosed soaring harness.
QUICK PIN — quick-release aircraft pin used to attach parts of a glider.
RATING — official certificate attesting to a pilot's skill level. Issued by hang gliding organizations such as the United States Hang Gliding Association.
RELATIVE WIND — air that flows over glider and pilot in flight. Relative wind is created by movement through the air.
RIB — alternate term for batten. Shaped aluminum tube that slips into sail to produce airfoil shape.
RIDGE LIFT — lift created by upward deflection of wind striking a ridge.
ROLL — banking or unbanking movement. Controlled by shifting of pilot's weight from side to side.
ROOT — center section of wing.
ROTOR — swirling air downwind of an obstacle.
SAFETY PIN — pin fastened through end of bolt to prevent nut from falling off.
SCRATCHING — working lift close to terrain.
SINK — descending air.
SLED RUN — flight in which not enough lift is encountered to extend flight.
SLIP — uncoordinated turn that results in high airspeed and sink rate.
SOARING — staying aloft by finding and maneuvering within rising air.
SPAN — as in "wingspan." Distance from wing tip to wing tip.
SKYING OUT — slang term for soaring very high.
SPECKING OUT — climbing so high that glider appears as a small speck overhead.
SPEEDBAR — specially-curved base tube that allows pilot to pull in farther than with a straight tube. Also improves comfort.
SPIRAL STABILITY (OR INSTABILITY) — tendency of a glider to hold or depart from a given bank angle during a turn.
SPIRAL DIVE — high speed slip that causes glider to descend extremely rapidly. Used by experienced pilots to escape from powerful lift.
STALL — loss of lift created by excessive angle of attack.
SWEEP — angling of wings so that tips are behind nose when seen from above or below. Aids pitch and yaw stability.
TANDEM — flying dual — pilot and passenger are suspended side by side in separate harnesses.
TANG — drilled metal plate used to attach cable to a tube.
TELL—TALE — streamer or ribbon used to check wind direction and speed.
THERMAL — rising column or bubble of warm air.
THIMBLE — stainless—steel, oval—shaped guide used to route cable around a fitting without kinking.
TIP — end of wing.
TOTAL ENERGY — special type of variometer that compensates for pilot's pitch inputs when gauging lift.
TRAILING EDGE — rear edge of wing.
TRILAM — trade name. Special plastic-coated sailcloth often used as leading edge material.
TWIST — change in wing's angle of incidence from root to tip. Also known as washout. Helps stall behaviour by allowing wing to stall progressively instead of all at once.
UNDERSURFACE — bottom surface of a glider's sail.
UPRIGHT — alternate term for downtube. May also be referred to as Leg.
USHPA — abbreviation for United States Hang Gliding & Paragliding Association.
VARIOMETER — instrument that measures vertical speed of sink or climb. Commonly abbreviated as vario.
VG — Abbreviation for Variable Geometry. System that allows pilot to vary tension of sail in flight to alter glider's performance and handling.
VNE — short for Velocity Never Exceed. Maximum allowable airspeed specified by a glider's designer.
VORTEX — contrail of swirling air created at wingtip by differential pressure above and below wing as an aircraft flies. Source of wake turbulence.
WAKE TURBULENCE — turbulence created by an aircraft's passage through the air.
WANG — aerobatic maneuver in which the glider rolls past vertical.
WASHOUT — same as twist.
WASHOUT TUBES — struts attached to leading edges near wingtips. Part of gliders' diverecovery system.
WEAK LINK — section of line used in hang glider towing systems. Breaks at specified load to protect glider from gusts and overloading.
WIND DUMMY — pilot who takes off before others so they can gauge conditions based on his flight.
WIND GRADIENT — slowing of air next to ground caused by surface friction. May cause rapid loss of airspeed when flying low.
WIND SHADOW — zone of still air behind obstacles such as trees, buildings or other obstructions.
WIND SOCK — tubular wind indicator made of fabric and mounted on pole.
WING LOADING — ratio of wing area to weight carried in flight. Determined by dividing glider's total wing area by the combined weight of pilot, glider and all gear that will be carried in flight.
WINGNUT — nut with arms that allow it to be threaded and unthreaded without using a wrench or other tools.
WINGOVER — same as wang.
WIRE LAUNCH — launch in which assistants stabilize glider by holding wires. Necessary in higher winds.
WONDERWIND — pleasant type of ridge lift that provides unexpectedly good altitude gains. Created when warm air is released from a valley as upper air cools.
YAW — movement of a glider or other aircraft in the vertical axis — i.e. — flat, "swinging" motion of wings from side to side.
XC — abbreviation for "cross country." Refers to extended soaring flight to a distant point.

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